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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: FileStreamRepository.html 973 2015-04-22 14:58:55Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.dellroad.stuff.io;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.io.File;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import java.io.FileInputStream;<a name="line.11"></a>
<span class="sourceLineNo">012</span>import java.io.IOException;<a name="line.12"></a>
<span class="sourceLineNo">013</span>import java.io.InputStream;<a name="line.13"></a>
<span class="sourceLineNo">014</span>import java.nio.file.FileAlreadyExistsException;<a name="line.14"></a>
<span class="sourceLineNo">015</span>import java.nio.file.Files;<a name="line.15"></a>
<span class="sourceLineNo">016</span>import java.nio.file.Path;<a name="line.16"></a>
<span class="sourceLineNo">017</span><a name="line.17"></a>
<span class="sourceLineNo">018</span>import org.slf4j.Logger;<a name="line.18"></a>
<span class="sourceLineNo">019</span>import org.slf4j.LoggerFactory;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>/**<a name="line.21"></a>
<span class="sourceLineNo">022</span> * Provides a file-based implementation of the {@link StreamRepository} interface with<a name="line.22"></a>
<span class="sourceLineNo">023</span> * the added feature of automated backups.<a name="line.23"></a>
<span class="sourceLineNo">024</span> *<a name="line.24"></a>
<span class="sourceLineNo">025</span> * &lt;p&gt;<a name="line.25"></a>
<span class="sourceLineNo">026</span> * Atomic updates are implemented using an {@link AtomicUpdateFileOutputStream}.<a name="line.26"></a>
<span class="sourceLineNo">027</span> * &lt;/p&gt;<a name="line.27"></a>
<span class="sourceLineNo">028</span> *<a name="line.28"></a>
<span class="sourceLineNo">029</span> * &lt;p&gt;<a name="line.29"></a>
<span class="sourceLineNo">030</span> * When backups are configured, the base file must be copied, not moved, to the first backup on update to avoid<a name="line.30"></a>
<span class="sourceLineNo">031</span> * a small window where the base file doesn't exist. This class uses {@linkplain Files#createLink hard links} to perform<a name="line.31"></a>
<span class="sourceLineNo">032</span> * this "copy" efficiently. This behavior can be altered by overriding {@link #copy copy()} on systems not supporting<a name="line.32"></a>
<span class="sourceLineNo">033</span> * hard links.<a name="line.33"></a>
<span class="sourceLineNo">034</span> * &lt;/p&gt;<a name="line.34"></a>
<span class="sourceLineNo">035</span> */<a name="line.35"></a>
<span class="sourceLineNo">036</span>public class FileStreamRepository implements StreamRepository {<a name="line.36"></a>
<span class="sourceLineNo">037</span><a name="line.37"></a>
<span class="sourceLineNo">038</span>    private final Logger log = LoggerFactory.getLogger(this.getClass());<a name="line.38"></a>
<span class="sourceLineNo">039</span><a name="line.39"></a>
<span class="sourceLineNo">040</span>    private final File file;<a name="line.40"></a>
<span class="sourceLineNo">041</span><a name="line.41"></a>
<span class="sourceLineNo">042</span>    private int numBackups;<a name="line.42"></a>
<span class="sourceLineNo">043</span>    private long timestamp;<a name="line.43"></a>
<span class="sourceLineNo">044</span><a name="line.44"></a>
<span class="sourceLineNo">045</span>    /**<a name="line.45"></a>
<span class="sourceLineNo">046</span>     * Primary constructor.<a name="line.46"></a>
<span class="sourceLineNo">047</span>     *<a name="line.47"></a>
<span class="sourceLineNo">048</span>     * @param file the file that will store the stream content<a name="line.48"></a>
<span class="sourceLineNo">049</span>     * @param numBackups number of backup copies to keep<a name="line.49"></a>
<span class="sourceLineNo">050</span>     * @throws IllegalArgumentException if {@code file} is null<a name="line.50"></a>
<span class="sourceLineNo">051</span>     * @throws IllegalArgumentException if {@code numBackups} is negative<a name="line.51"></a>
<span class="sourceLineNo">052</span>     */<a name="line.52"></a>
<span class="sourceLineNo">053</span>    public FileStreamRepository(File file, int numBackups) {<a name="line.53"></a>
<span class="sourceLineNo">054</span>        if (file == null)<a name="line.54"></a>
<span class="sourceLineNo">055</span>            throw new IllegalArgumentException("null file");<a name="line.55"></a>
<span class="sourceLineNo">056</span>        if (numBackups &lt; 0)<a name="line.56"></a>
<span class="sourceLineNo">057</span>            throw new IllegalArgumentException("negative numBackups");<a name="line.57"></a>
<span class="sourceLineNo">058</span>        this.file = file;<a name="line.58"></a>
<span class="sourceLineNo">059</span>        this.numBackups = numBackups;<a name="line.59"></a>
<span class="sourceLineNo">060</span>    }<a name="line.60"></a>
<span class="sourceLineNo">061</span><a name="line.61"></a>
<span class="sourceLineNo">062</span>    /**<a name="line.62"></a>
<span class="sourceLineNo">063</span>     * Convenience constructor for the case where no backup copies are needed.<a name="line.63"></a>
<span class="sourceLineNo">064</span>     *<a name="line.64"></a>
<span class="sourceLineNo">065</span>     * &lt;p&gt;<a name="line.65"></a>
<span class="sourceLineNo">066</span>     * Equivalent to:<a name="line.66"></a>
<span class="sourceLineNo">067</span>     * &lt;blockquote&gt;&lt;code&gt;<a name="line.67"></a>
<span class="sourceLineNo">068</span>     *  FileStreamRepository(file, 0);<a name="line.68"></a>
<span class="sourceLineNo">069</span>     * &lt;/code&gt;&lt;/blockquote&gt;<a name="line.69"></a>
<span class="sourceLineNo">070</span>     */<a name="line.70"></a>
<span class="sourceLineNo">071</span>    public FileStreamRepository(File file) {<a name="line.71"></a>
<span class="sourceLineNo">072</span>        this(file, 0);<a name="line.72"></a>
<span class="sourceLineNo">073</span>    }<a name="line.73"></a>
<span class="sourceLineNo">074</span><a name="line.74"></a>
<span class="sourceLineNo">075</span>    /**<a name="line.75"></a>
<span class="sourceLineNo">076</span>     * Get the configured {@link File}.<a name="line.76"></a>
<span class="sourceLineNo">077</span>     *<a name="line.77"></a>
<span class="sourceLineNo">078</span>     * @return the file that stores the stream content (same as given to constructor)<a name="line.78"></a>
<span class="sourceLineNo">079</span>     */<a name="line.79"></a>
<span class="sourceLineNo">080</span>    public final File getFile() {<a name="line.80"></a>
<span class="sourceLineNo">081</span>        return this.file;<a name="line.81"></a>
<span class="sourceLineNo">082</span>    }<a name="line.82"></a>
<span class="sourceLineNo">083</span><a name="line.83"></a>
<span class="sourceLineNo">084</span>    /**<a name="line.84"></a>
<span class="sourceLineNo">085</span>     * Get the configured number of backup files.<a name="line.85"></a>
<span class="sourceLineNo">086</span>     *<a name="line.86"></a>
<span class="sourceLineNo">087</span>     * @return the number of backup files to maintain<a name="line.87"></a>
<span class="sourceLineNo">088</span>     */<a name="line.88"></a>
<span class="sourceLineNo">089</span>    public final int getNumBackups() {<a name="line.89"></a>
<span class="sourceLineNo">090</span>        return this.numBackups;<a name="line.90"></a>
<span class="sourceLineNo">091</span>    }<a name="line.91"></a>
<span class="sourceLineNo">092</span><a name="line.92"></a>
<span class="sourceLineNo">093</span>    /**<a name="line.93"></a>
<span class="sourceLineNo">094</span>     * Change the number of backup files to maintain.<a name="line.94"></a>
<span class="sourceLineNo">095</span>     *<a name="line.95"></a>
<span class="sourceLineNo">096</span>     * &lt;p&gt;<a name="line.96"></a>
<span class="sourceLineNo">097</span>     * If the number of backups is reduced, the "extra" backup files are not touched.<a name="line.97"></a>
<span class="sourceLineNo">098</span>     *<a name="line.98"></a>
<span class="sourceLineNo">099</span>     * @param numBackups number of backup files<a name="line.99"></a>
<span class="sourceLineNo">100</span>     * @throws IllegalArgumentException if {@code numBackups} is less than zero<a name="line.100"></a>
<span class="sourceLineNo">101</span>     */<a name="line.101"></a>
<span class="sourceLineNo">102</span>    public void setNumBackups(int numBackups) {<a name="line.102"></a>
<span class="sourceLineNo">103</span>        this.numBackups = numBackups;<a name="line.103"></a>
<span class="sourceLineNo">104</span>    }<a name="line.104"></a>
<span class="sourceLineNo">105</span><a name="line.105"></a>
<span class="sourceLineNo">106</span>    @Override<a name="line.106"></a>
<span class="sourceLineNo">107</span>    public InputStream getInputStream() throws IOException {<a name="line.107"></a>
<span class="sourceLineNo">108</span>        return new FileInputStream(this.file);<a name="line.108"></a>
<span class="sourceLineNo">109</span>    }<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span>    @Override<a name="line.111"></a>
<span class="sourceLineNo">112</span>    public AtomicUpdateFileOutputStream getOutputStream() throws IOException {<a name="line.112"></a>
<span class="sourceLineNo">113</span>        String tempName = this.file.getName();<a name="line.113"></a>
<span class="sourceLineNo">114</span>        while (tempName.length() &lt; 3)<a name="line.114"></a>
<span class="sourceLineNo">115</span>            tempName += "z";<a name="line.115"></a>
<span class="sourceLineNo">116</span>        final File tempFile = File.createTempFile(tempName, null, this.file.getParentFile());<a name="line.116"></a>
<span class="sourceLineNo">117</span>        return new AtomicUpdateFileOutputStream(this.file, tempFile) {<a name="line.117"></a>
<span class="sourceLineNo">118</span>            @Override<a name="line.118"></a>
<span class="sourceLineNo">119</span>            public void close() throws IOException {<a name="line.119"></a>
<span class="sourceLineNo">120</span>                synchronized (FileStreamRepository.this) {<a name="line.120"></a>
<span class="sourceLineNo">121</span><a name="line.121"></a>
<span class="sourceLineNo">122</span>                    // Rotate backups<a name="line.122"></a>
<span class="sourceLineNo">123</span>                    FileStreamRepository.this.rotateBackups();<a name="line.123"></a>
<span class="sourceLineNo">124</span><a name="line.124"></a>
<span class="sourceLineNo">125</span>                    // Save and update file<a name="line.125"></a>
<span class="sourceLineNo">126</span>                    super.close();<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>
<span class="sourceLineNo">128</span>                    // Update timestamp<a name="line.128"></a>
<span class="sourceLineNo">129</span>                    FileStreamRepository.this.timestamp = this.getTimestamp();<a name="line.129"></a>
<span class="sourceLineNo">130</span>                }<a name="line.130"></a>
<span class="sourceLineNo">131</span>            }<a name="line.131"></a>
<span class="sourceLineNo">132</span>        };<a name="line.132"></a>
<span class="sourceLineNo">133</span>    }<a name="line.133"></a>
<span class="sourceLineNo">134</span><a name="line.134"></a>
<span class="sourceLineNo">135</span>    /**<a name="line.135"></a>
<span class="sourceLineNo">136</span>     * Get the last modification timestamp of the target file as known to this instance.<a name="line.136"></a>
<span class="sourceLineNo">137</span>     *<a name="line.137"></a>
<span class="sourceLineNo">138</span>     * &lt;p&gt;<a name="line.138"></a>
<span class="sourceLineNo">139</span>     * This returns the modification timestamp as known by this instance; it does not ask the filesystem<a name="line.139"></a>
<span class="sourceLineNo">140</span>     * for the actual last modification timestamp. So if the two are different, then the file has<a name="line.140"></a>
<span class="sourceLineNo">141</span>     * been updated by some external process. In other words, this returns the modification timestamp<a name="line.141"></a>
<span class="sourceLineNo">142</span>     * of the underlying file as it was at the time of the most recent update.<a name="line.142"></a>
<span class="sourceLineNo">143</span>     *<a name="line.143"></a>
<span class="sourceLineNo">144</span>     * @return file's last modification timestamp as known by this instance,<a name="line.144"></a>
<span class="sourceLineNo">145</span>     *  or zero if the file has not yet been successfully written to<a name="line.145"></a>
<span class="sourceLineNo">146</span>     */<a name="line.146"></a>
<span class="sourceLineNo">147</span>    public synchronized long getFileTimestamp() {<a name="line.147"></a>
<span class="sourceLineNo">148</span>        return this.timestamp;<a name="line.148"></a>
<span class="sourceLineNo">149</span>    }<a name="line.149"></a>
<span class="sourceLineNo">150</span><a name="line.150"></a>
<span class="sourceLineNo">151</span>    /**<a name="line.151"></a>
<span class="sourceLineNo">152</span>     * Generate a backup file name.<a name="line.152"></a>
<span class="sourceLineNo">153</span>     *<a name="line.153"></a>
<span class="sourceLineNo">154</span>     * &lt;p&gt;<a name="line.154"></a>
<span class="sourceLineNo">155</span>     * The implementation in {@link FileStreamRepository} returns a file with the same name as {@code file}<a name="line.155"></a>
<span class="sourceLineNo">156</span>     * plus a suffix &lt;code&gt;.1&lt;/code&gt;,  &lt;code&gt;.2&lt;/code&gt;, &lt;code&gt;.3&lt;/code&gt;, etc. corresponding to {@code index}.<a name="line.156"></a>
<span class="sourceLineNo">157</span>     * Subclasses may override as desired.<a name="line.157"></a>
<span class="sourceLineNo">158</span>     *<a name="line.158"></a>
<span class="sourceLineNo">159</span>     * @param file the file that stores the current stream content (i.e., from {@link #getFile})<a name="line.159"></a>
<span class="sourceLineNo">160</span>     * @param index backup index, always greater than or equal to 1<a name="line.160"></a>
<span class="sourceLineNo">161</span>     */<a name="line.161"></a>
<span class="sourceLineNo">162</span>    protected File getBackupFile(File file, int index) {<a name="line.162"></a>
<span class="sourceLineNo">163</span>        return new File(file.toString() + "." + index);<a name="line.163"></a>
<span class="sourceLineNo">164</span>    }<a name="line.164"></a>
<span class="sourceLineNo">165</span><a name="line.165"></a>
<span class="sourceLineNo">166</span>    /**<a name="line.166"></a>
<span class="sourceLineNo">167</span>     * Copy, via hard link if possible, a file. If the two files are the same, nothing should be done.<a name="line.167"></a>
<span class="sourceLineNo">168</span>     *<a name="line.168"></a>
<span class="sourceLineNo">169</span>     * &lt;p&gt;<a name="line.169"></a>
<span class="sourceLineNo">170</span>     * The implementation in {@link FileStreamRepository} uses {@linkplain Files#createLink hard links}.<a name="line.170"></a>
<span class="sourceLineNo">171</span>     * Subclasses must override this method if the platform does not support hard links.<a name="line.171"></a>
<span class="sourceLineNo">172</span>     * &lt;/p&gt;<a name="line.172"></a>
<span class="sourceLineNo">173</span>     *<a name="line.173"></a>
<span class="sourceLineNo">174</span>     * @param src source file<a name="line.174"></a>
<span class="sourceLineNo">175</span>     * @param dst destination file<a name="line.175"></a>
<span class="sourceLineNo">176</span>     * @throws IOException if unsuccessful<a name="line.176"></a>
<span class="sourceLineNo">177</span>     */<a name="line.177"></a>
<span class="sourceLineNo">178</span>    protected void copy(File src, File dst) throws IOException {<a name="line.178"></a>
<span class="sourceLineNo">179</span>        final Path srcPath = src.toPath();<a name="line.179"></a>
<span class="sourceLineNo">180</span>        final Path dstPath = dst.toPath();<a name="line.180"></a>
<span class="sourceLineNo">181</span>        try {<a name="line.181"></a>
<span class="sourceLineNo">182</span>            if (dst.exists() &amp;&amp; Files.isSameFile(srcPath, dstPath))<a name="line.182"></a>
<span class="sourceLineNo">183</span>                return;<a name="line.183"></a>
<span class="sourceLineNo">184</span>        } catch (IOException e) {<a name="line.184"></a>
<span class="sourceLineNo">185</span>            // ignore<a name="line.185"></a>
<span class="sourceLineNo">186</span>        }<a name="line.186"></a>
<span class="sourceLineNo">187</span>        try {<a name="line.187"></a>
<span class="sourceLineNo">188</span>            Files.createLink(dstPath, srcPath);<a name="line.188"></a>
<span class="sourceLineNo">189</span>        } catch (FileAlreadyExistsException e) {<a name="line.189"></a>
<span class="sourceLineNo">190</span>            dst.delete();<a name="line.190"></a>
<span class="sourceLineNo">191</span>            Files.createLink(dstPath, srcPath);<a name="line.191"></a>
<span class="sourceLineNo">192</span>        }<a name="line.192"></a>
<span class="sourceLineNo">193</span>    }<a name="line.193"></a>
<span class="sourceLineNo">194</span><a name="line.194"></a>
<span class="sourceLineNo">195</span>    /**<a name="line.195"></a>
<span class="sourceLineNo">196</span>     * Rotate backup files.<a name="line.196"></a>
<span class="sourceLineNo">197</span>     */<a name="line.197"></a>
<span class="sourceLineNo">198</span>    private synchronized void rotateBackups() throws IOException {<a name="line.198"></a>
<span class="sourceLineNo">199</span><a name="line.199"></a>
<span class="sourceLineNo">200</span>        // Generate file names: 0 -&gt; "file", 1 -&gt; "file.1", 2 -&gt; "file.2", etc.<a name="line.200"></a>
<span class="sourceLineNo">201</span>        File[] files = new File[this.numBackups + 1];<a name="line.201"></a>
<span class="sourceLineNo">202</span>        files[0] = this.getFile();<a name="line.202"></a>
<span class="sourceLineNo">203</span>        for (int i = 0; i &lt; this.numBackups; i++)<a name="line.203"></a>
<span class="sourceLineNo">204</span>            files[i + 1] = this.getBackupFile(this.getFile(), i + 1);<a name="line.204"></a>
<span class="sourceLineNo">205</span><a name="line.205"></a>
<span class="sourceLineNo">206</span>        // Rotate backups<a name="line.206"></a>
<span class="sourceLineNo">207</span>        for (int i = this.numBackups - 1; i &gt;= 0; i--) {<a name="line.207"></a>
<span class="sourceLineNo">208</span>            final File src = files[i];<a name="line.208"></a>
<span class="sourceLineNo">209</span>            final File dst = files[i + 1];<a name="line.209"></a>
<span class="sourceLineNo">210</span><a name="line.210"></a>
<span class="sourceLineNo">211</span>            // For the first backup, create a copy so there's no window when the target file does not exist<a name="line.211"></a>
<span class="sourceLineNo">212</span>            if (i == 0) {<a name="line.212"></a>
<span class="sourceLineNo">213</span>                try {<a name="line.213"></a>
<span class="sourceLineNo">214</span>                    this.copy(src, dst);<a name="line.214"></a>
<span class="sourceLineNo">215</span>                } catch (IOException e) {<a name="line.215"></a>
<span class="sourceLineNo">216</span>                    this.log.warn("failed to copy `" + src + "' to backup `" + dst + "'", e);<a name="line.216"></a>
<span class="sourceLineNo">217</span>                }<a name="line.217"></a>
<span class="sourceLineNo">218</span>            } else<a name="line.218"></a>
<span class="sourceLineNo">219</span>                src.renameTo(dst);      // OK if this fails, that means the backup file doesn't exist yet<a name="line.219"></a>
<span class="sourceLineNo">220</span>        }<a name="line.220"></a>
<span class="sourceLineNo">221</span>    }<a name="line.221"></a>
<span class="sourceLineNo">222</span>}<a name="line.222"></a>
<span class="sourceLineNo">223</span><a name="line.223"></a>




























































</pre>
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